Laminar mass transport enhancement of gaseous mixing and catalytic reaction in a semi T-shaped microreactor was examined via numerical simulations. The mathematical model considers a multicomponent species mixture with multi-step heterogeneous reactions and comprises of conservation equations of mass, momentum, species and energy. The mass transport performance is evaluated by modeling the catalytic reaction of a mixture of methane and air. Several innovative channel designs are proposed to improve mixing and reaction kinetics, e.g. innovative circular and rectangular configuration, flow splitting, redirection, recirculation and impingement. The results suggest that the rectangular design yields better conversion rate than the rate obtained with its circular counterpart. Flow splitting and impingement are found to be beneficial to improve mixing and reaction rate; albeit this imposes a greater pressure drop penalty. Effect of pre-mixing is also investigated with regard to the mass transport performance. Finally, advantages and limitations of each design are discussed in the light of the numerical results. (C) 2012 Elsevier B.V. All rights reserved.